import { describe, it, expect } from "vitest";

/**
 * Standings Snapshots Tests
 * Phase 4.2: Test snapshot creation and 7-day comparison logic
 *
 * These are unit tests that verify the snapshot logic works correctly.
 * Integration tests that use the actual database are in the e2e test suite.
 */

/**
 * Helper function to simulate 7-day rank change calculation
 * This mirrors the logic in getSevenDayStandingsChange
 */
function calculateSevenDayChange(
  currentRank: number,
  sevenDayOldRank: number | null
): number {
  if (sevenDayOldRank === null) {
    return 0; // No snapshot from 7 days ago
  }
  // Positive number = improvement (was 5th, now 3rd = +2)
  // Negative number = decline (was 3rd, now 5th = -2)
  return sevenDayOldRank - currentRank;
}

/**
 * Helper function to simulate snapshot deduplication logic
 * This mirrors the logic in createDailySnapshot
 */
function shouldCreateSnapshot(
  existingSnapshotDate: string | null,
  today: string
): boolean {
  // Don't create if snapshot already exists for today
  return existingSnapshotDate !== today;
}

describe("Standings Snapshots", () => {
  describe("7-Day Rank Change Calculation", () => {
    it("should calculate positive change when rank improves", () => {
      const change = calculateSevenDayChange(1, 3);
      expect(change).toBe(2); // Moved from 3rd to 1st = +2
    });

    it("should calculate negative change when rank declines", () => {
      const change = calculateSevenDayChange(5, 2);
      expect(change).toBe(-3); // Moved from 2nd to 5th = -3
    });

    it("should return 0 when rank stays the same", () => {
      const change = calculateSevenDayChange(2, 2);
      expect(change).toBe(0);
    });

    it("should return 0 when no snapshot exists from 7 days ago", () => {
      const change = calculateSevenDayChange(1, null);
      expect(change).toBe(0);
    });

    it("should handle large rank improvements", () => {
      const change = calculateSevenDayChange(1, 10);
      expect(change).toBe(9); // Moved from 10th to 1st = +9
    });

    it("should handle large rank declines", () => {
      const change = calculateSevenDayChange(10, 1);
      expect(change).toBe(-9); // Moved from 1st to 10th = -9
    });
  });

  describe("Snapshot Deduplication", () => {
    it("should create snapshot when no existing snapshot for today", () => {
      const today = "2025-01-13";
      const shouldCreate = shouldCreateSnapshot(null, today);
      expect(shouldCreate).toBe(true);
    });

    it("should not create snapshot when snapshot already exists for today", () => {
      const today = "2025-01-13";
      const existingDate = "2025-01-13";
      const shouldCreate = shouldCreateSnapshot(existingDate, today);
      expect(shouldCreate).toBe(false);
    });

    it("should create snapshot when last snapshot was yesterday", () => {
      const today = "2025-01-13";
      const existingDate = "2025-01-12";
      const shouldCreate = shouldCreateSnapshot(existingDate, today);
      expect(shouldCreate).toBe(true);
    });

    it("should create snapshot when last snapshot was 7 days ago", () => {
      const today = "2025-01-13";
      const existingDate = "2025-01-06";
      const shouldCreate = shouldCreateSnapshot(existingDate, today);
      expect(shouldCreate).toBe(true);
    });
  });

  describe("Snapshot Data Integrity", () => {
    it("should preserve all tiebreaker data in snapshot", () => {
      const standing = {
        totalPoints: 150.5,
        currentRank: 1,
        firstPlaceCount: 2,
        secondPlaceCount: 1,
        thirdPlaceCount: 0,
        fourthPlaceCount: 0,
        fifthPlaceCount: 0,
        sixthPlaceCount: 0,
        seventhPlaceCount: 0,
        eighthPlaceCount: 0,
        participantsRemaining: 5,
      };

      // Snapshot should contain all the same data
      const snapshot = {
        totalPoints: standing.totalPoints,
        rank: standing.currentRank,
        firstPlaceCount: standing.firstPlaceCount,
        secondPlaceCount: standing.secondPlaceCount,
        thirdPlaceCount: standing.thirdPlaceCount,
        fourthPlaceCount: standing.fourthPlaceCount,
        fifthPlaceCount: standing.fifthPlaceCount,
        sixthPlaceCount: standing.sixthPlaceCount,
        seventhPlaceCount: standing.seventhPlaceCount,
        eighthPlaceCount: standing.eighthPlaceCount,
        participantsRemaining: standing.participantsRemaining,
      };

      expect(snapshot.totalPoints).toBe(standing.totalPoints);
      expect(snapshot.rank).toBe(standing.currentRank);
      expect(snapshot.firstPlaceCount).toBe(standing.firstPlaceCount);
      expect(snapshot.participantsRemaining).toBe(standing.participantsRemaining);
    });
  });

  describe("Movement Scenarios", () => {
    it("should handle team moving from last to first", () => {
      const scenarios = [
        { current: 1, old: 8, expected: 7 }, // Last to first = +7
        { current: 8, old: 1, expected: -7 }, // First to last = -7
      ];

      scenarios.forEach(({ current, old, expected }) => {
        const change = calculateSevenDayChange(current, old);
        expect(change).toBe(expected);
      });
    });

    it("should handle multiple teams with different movements", () => {
      const teams = [
        { id: "A", currentRank: 1, oldRank: 3, expectedChange: 2 },
        { id: "B", currentRank: 2, oldRank: 1, expectedChange: -1 },
        { id: "C", currentRank: 3, oldRank: 2, expectedChange: -1 },
        { id: "D", currentRank: 4, oldRank: null, expectedChange: 0 },
      ];

      teams.forEach((team) => {
        const change = calculateSevenDayChange(team.currentRank, team.oldRank);
        expect(change).toBe(team.expectedChange);
      });
    });
  });

  describe("Historical Tracking", () => {
    it("should maintain chronological order of snapshots", () => {
      const snapshots = [
        { date: "2025-01-13", rank: 1 },
        { date: "2025-01-12", rank: 2 },
        { date: "2025-01-11", rank: 3 },
        { date: "2025-01-10", rank: 2 },
        { date: "2025-01-09", rank: 1 },
      ];

      // Should be sorted by date descending (newest first)
      const sorted = [...snapshots].toSorted((a, b) =>
        b.date.localeCompare(a.date)
      );

      expect(sorted[0].date).toBe("2025-01-13");
      expect(sorted[4].date).toBe("2025-01-09");
    });

    it("should show rank progression over time", () => {
      const history = [
        { date: "2025-01-09", rank: 5, points: 50 },
        { date: "2025-01-10", rank: 4, points: 75 },
        { date: "2025-01-11", rank: 3, points: 100 },
        { date: "2025-01-12", rank: 2, points: 125 },
        { date: "2025-01-13", rank: 1, points: 150 },
      ];

      // Verify progression shows improvement
      for (let i = 1; i < history.length; i++) {
        expect(history[i].rank).toBeLessThan(history[i - 1].rank);
        expect(history[i].points).toBeGreaterThan(history[i - 1].points);
      }
    });
  });
});